1. Field of the Invention
The present invention relates to an apparatus and a method which protect the header of an asynchronous transfer mode (ATM) cell from the burst error by using reed-solomon RS error correcting code in order to compensate the loss of the ATM cell on the link of the ATM cell and prevent the increase of the overhead by applying a header error correction HEC bit to a forward error correction code FEC.
2. Description of the Prior Art
In the priority art, the conventional methods protecting the header of an ATM cell are classified according to the following two types: firstly, a method using the Interleaver/Deinterleaver technique and, secondly, another method using the FEC technique.
The method using the Interleaver/Deinterleaver technique generates random errors by applying the Interleaver/Deinterleaver technique to an ATM header and distributing the burst errors, and corrects one bit; error generating among ATM headers of five bits. However, this method requires many memories in order to process the burst errors generating the ATM header and has a problem that the processing time is delayed.
On the other hand, the method of using the FEC technique of the conventional art further requires an overhead bit and has a problem reducing the frequency use efficiency.
In order to settle the problems, it is an object of the present invention to provide an apparatus and a method for protecting the ATM header on a channel, of which noise has the burst error characteristics, by using reed-solomon (RS) error correction code without changing the structure of the conventional ATM cell.
The apparatus of the present invention includes an ATM exchanger for generating an ATM cell; an encoder for dividing the ATM cell into an ATM header and an ATM payload by deframing and reverse-multiplexing the ATM cell, and for encoding the overhead bit of the ATM header by using a RS error correction code without changing the structure of a conventional ATM cell for multiplexing the ATM header by inserting it into a header error correction bit; a modulator for framing the ATM header and the ATM payload, which are inputted from the encoder, in type of the physical layer convergence protocol and for modulating them; a demodulator for demodulating the modulated data of the modulator; and a decoder for dividing the ATM cell into the ATM header and the ATM payload by reverse-multiplexing it by deframing the demodulated data of the demodulator in type of the physical layer convergence protocol, and for decoding and correcting the burst error generated in the ATM header in order to multiplex the reordered ATM header and transmit it to the ATM exchanger.
The method of the present invention for protecting an ATM header on an encoding channel of which noise has the burst error characteristics comprises the first step of initializing the counter value of an ATM cell; the second step of dividing an ATM header and an ATM payload from the inputted ATM cell, and of encoding an error correction code by comparing the counter value of the ATM cell with the counter value of a physical layer convergence protocol frame after abandoning the ATM cell or correcting the ATM header according to the number of errors of the ATM header by using the header error correction HEC bite; and the third step of reordering the ATM header and the ATM payload and of outputting the reordered physical layer convergence protocol frame.
Also, the mode for protecting an ATM header on a decoding channel of which noise has the burst error characteristics comprises the first step of initializing the counter value of an ATM cell; the second step of dividing an ATM header and an ATM payload from the inputted ATM cell, and of correcting the generated error by comparing the counter value of the ATM cell with the counter value of a physical layer convergence protocol frame and decoding an error correction code after buffering the ATM header; and the third step of generating a header error correction bite by reordering the ATM header and the ATM payload and of outputting the reordered ATM cell in type of the reordered physical layer convergence protocol frame.